1. Field of the Invention
The present invention generally relates to wireless communication devices that are configured for operation using a plurality of communication bands and more particularly to GPS enabled multi-band wireless communication devices.
2. Background Information
A conventional hand-held Global Positioning System (GPS) device provides positional information, related to the location of the GPS device, by receiving and processing GPS band signals from a GPS system. Although such positional information can be quite useful, it is not always convenient to carry a conventional GPS device. Especially, if the user must also carry around one or more other portable devices, such as a laptop, wireless handset, Personal Digital Assistant (PDA), or other portable device on which users now depend. It is therefore desirable that a GPS positioning function be integrated within one of these other portable devices.
Unfortunately, the integration of GPS technology with other portable devices has proven difficult. For example, three methods for adding GPS capability to a wireless handset have been implemented, but have proven unsatisfactory in use.
The first method is to add GPS capability in a wireless handset by adding a separate antenna for GPS reception. Since the wireless network antenna is not modified, network communications quality is not adversely affected. However, as mobile handsets for wireless networks have become much smaller, less space is available in the handset housing to accommodate a separate, custom-designed GPS antenna. Furthermore, a GPS antenna disposed within the handset housing typically suffers from a number of reception problems. For example, poor reception can be caused by electromagnetic shielding within the handset housing and by the handset housing itself. Adjusting the electromagnetic shielding to accommodate the GPS antenna can cause substantial redesign and testing of the handset. Also, adding a separate antenna and its associated circuitry to the wireless handset adds expense and design complexity.
The second method is to add GPS capability to a wireless handset by enabling the existing network antenna on the wireless handset to adequately receive a GPS band signal. For example, a typical dual-band antenna may be constructed to receive a PCS signal at approximately 1900 MHz and a cellular signal at approximately 800 MHz. It may therefore be possible that the existing dual-band antenna may be able to receive a GPS signal at approximately 1575 MHz. However, the GPS signal is at a non-resonant frequency for the dual-band antenna, so the received GPS signal would be less than optimal resulting in degraded signal transfer. In this regard, known dual-band antenna systems are not able to receive a GPS signal with sufficient strength and quality to implement a robust GPS location functionality on a wireless handset.
The third method is to add GPS capability to a wireless handset using a tri-band antenna. A tri-band antenna is constructed to receive the cellular, PCS and GPS frequencies, for example. Due to the limitations of antenna design, however, such an antenna normally compromises either the cellular or PCS performance, or both. Using a tri-band antenna also adds substantial extra cost to the antenna.